This invention relates to an electrode for electrical discharge machining, particularly an electrode for electrical discharge used for diesinking and to a process for manufacturing the same.
As the electrode for electrical discharge machining used for diesinking, those comprising graphite/beryllium/copper alloys processed by a three-dimensional machine tool are generally used. However, those electrodes for electrical discharge machining which primarily comprises graphite etc. suffer problems that they not only require considerable time for the machining with poor accuracy, but also expensive machinery, leading to rise in cost. Under such circumstances, the present inventors have previously developed an electrode for electrical discharge machining, which comprises an electrode member produced by subjecting a base and binder of gypsum hemihydrate powder and a filler of conductive metal powder to modeling and/or molding and setting into a desired form of electrode, followed by impregnation with an electrically conductive solution such as a graphite suspension (micro particles of natural graphite suspended in ammonia solution; e.g. "HITASOL", trade name, manufactured by Hitachi Chemical Co., Ltd.) and the like to enhance mutual continuity in the conductivity of the former conductive metal powder dispersed as a filler in the electrode member and filed as Japanese Patent Application No. 46069/1989. Nevertheless, in an attempt of machining various types of products by means of electrical discharge machining using the electrode as disclosed in the previously filed Patent Application, problem has arisen that if such electrode is used as such, its durability is questionable due to the brittleness of the material; only a very low amperage of machining current can be applied to the electrode since a current cannot be charged at high density due to the local sparsity in the mutual continuity between the metal powder particles to easily cause internal discharge. Besides, if such electrode is used for the machining of a subtle dental crown and bridge comprising a hard material such as titanium, the electrode wears off quickly and the desired product cannot be obtained due to insufficient machining accuracy.